The present invention relates to a flat knitting machine comprising a transfer jack bed (hereinafter it is referred to as xe2x80x9cTR jack bedxe2x80x9d) in which a number of transfer jacks (hereinafter they are referred to as xe2x80x9cTR jackxe2x80x9d) each having a loop retaining portion at a front end thereof are implanted and which is arranged over needle beds, and a transfer cam mechanism for transferring the loop between the TR jacks of the TR jack bed and the needles of the needle beds, and to a loop transfer method.
A flat knitting machine comprising a pair of front and back needle beds holding needles in such a manner as to be advanced and retracted in needle grooves formed on upper surfaces of the needle beds, at least one of which is movable horizontally with respect to the other needle bed, and at least one transfer jack bed located over the at least one needle bed and holding transfer jacks in such a manner as to freely advance and retract in the grooves formed on an upper surface thereof is disclosed by Japanese Patent No. 2794144. In the flat knitting machine disclosed in this publication, the TR jack bed and the needle beds are so structured that they can be racked longitudinally relative to each other to transfer a loop between the needles of the front and back needle beds and between the needle of the needle bed and the TR jack of the TR jack bed. This flat knitting machine thus structured enables a loop retained by the needle of the needle bed to be transferred to an adjacent needle of the same needle bed by transferring the loop retained by the needle of the needle bed to the TR jack of the TR jack bed, first; then racking the TR jack bed; and then transferring the loop retained by the TR jack to the adjacent needle of the needle bed.
When the TR jack bed and the needle bed are racked relative to each other in the state in which the loop transferred from the needle to the TR jack is kept retained by the TR jack, upper and lower yarn portions of the loop retained by the loop retaining portion of the TR jack are pulled in the racking direction. As the racking distance increases, the distance between the upper and lower yarn portions of the loop decreases and resultantly the space in the loop for the needle to be advanced into becomes narrower. As a result of this, there arises the drawback that the needle hook to be advanced into the loop may collide with the upper and lower yarn portions of the loop to cause possible yarn breakage or stitch drop. Although the space in the loop for the needle to be advanced into can be widened by increasing thickness of the loop retaining portion of the TR jack with respect to a height direction thereof, there could then arise another drawback that when fine loops are formed in knitting, a burden is placed on the loops to cause possible yarn breakage.
For solving the problem noted above, the applicant of this application previously proposed a flat knitting machine disclosed in Japanese Laid-open (Unexamined) Patent Publication No. Hei 11 (1999)-323703. In the flat knitting machine disclosed by Japanese Laid-open (Unexamined) Patent Publication No. Hei 11 (1999)-323703, when the needle is advanced into the loop retained by the TR jack, to transfer the loop from the TR jack to the needle, the TR jack is advanced and retracted horizontally so that when a back side of the needle hook is advanced into the loop, the TR jack is moved in the direction in which the loop is moved to the back side of the needle hook, while on the other hand, when a front side of the needle hook is advanced into the loop, the TR jack is moved in the direction in which the loop is moved to the front side of the needle hook.
In the flat knitting machine disclosed by Japanese Laid-open (Unexamined) Patent Publication No. Hei 11 (1999)-323703, when the loop is transferred between the TR jack bed and the needle bed immediately under the TR jack bed, the TR jack bed is advanced to a position beyond a center line of a needle bed gap once and then is retracted to a position on the center line of the needle bed gap, so that the needle hook is advanced into the loop on the loop retaining portion of the TR jack. After that, when the loop is transferred between the TR jack bed and the back needle bed confronting it across the needle bed gap, the TR jack is retracted from the center line of the needle bed gap once and then is put back to the position on the center line of the needle bed gap, so that the needle hook is advanced into the loop. In the flat knitting machine disclosed by Japanese Laid-open (Unexamined) Patent Publication No. Hei 11 (1999)-323703, in order for the needle hooks to be advanced into the loops, a track for the TR jacks for the needles of the front needle bed and a track for the TR jacks for the back needle bed are separately provided in carriages. This enables the space in the loop for the needle to be advanced into to be widened without any need to increase the thickness of the loop retaining portion of the TR jack with respect to a height direction thereof.
It is the object of the present invention to disclose a flat knitting machine that can provide a reliable transfer of loop with a reduced burden on the loop in the transfer of loop using a common track for the needles of the front needle bed and for the needles of the back needle bed, and a loop transfer method.
In order to solve the problem noted above, the present invention provides a flat knitting machine with a loop transfer mechanism comprising a pair of front and back needle beds holding needles in such a manner as to freely advance and retract in grooves formed in upper surfaces of the needle beds, at least one of which is movable laterally relative to the other needle bed, and at least one transfer jack bed provided over the at least one needle bed and holding transfer jacks in such a manner as to freely advance and retract in grooves in upper surface of the at least one transfer jack bed, wherein each transfer jack has, on a front end portion thereof, a loop retraining portion which is held in such a manner as to be movable between its lowered position and its raised position in its advanced position on a center line of a needle bed gap between the front and back needle beds; and wherein there is provided transfer jack control means for making such a control that when a loop is transferred from the transfer jack to the needle, the loop retaining portion of the transfer jack put in its advanced position is moved down to its lowered position, first; then, a back side of a needle hook of the needle is made to go into the loop retained on the loop retaining portion of the transfer jack; then the loop retaining portion is raised up to its raised position; and thereafter, a front side of the needle hook of the needle is made to go into the loop. With the construction of the present invention, when the loop is transferred from the TR jack to the needle, the loop retaining portion of the transfer jack put in its advanced position is moved down to its lowered position, first, and, then, the back side of the needle hook goes into the loop retained on the loop retaining portion of the transfer jack. This allows the back side of the needle hook to go into the loop without colliding with the lower yarn portion of the loop crossing beneath the loop retaining portion. Then, after the loop retaining portion is raised up to its raised position, the front side of the needle hook goes into the loop. This allows the front side of the needle hook to go into the loop without colliding with the upper yarn portion of the loop crossing over the loop retaining portion. Thus, in the flat knitting machine of the present invention, the transfer of the loop between the TR jack and the front bed and the transfer of the loop between the TR jack and the back bed is effected through the use of the common track. Also, the loop is lowered in position when the TR jack is retracted from the loop, so that the burden put on the loop is reduced.
It is one of the characteristic feature of the present invention that the transfer jack control means comprises an advancing-and-retracting control cam for controlling the transfer jack so as to be advanced toward and retracted from the center line of the needle bed gap; a clearing cam for controlling the loop retaining portion of the transfer jack put in its advanced position, when the loop is transferred from the transfer jack to the needle, so as to be moved down to its lowered position before the back side of the needle hook of the needle goes into the loop retained on the loop retaining portion of the transfer jack; and a raising cam, located at a rear side of the clearing cam with respect to a moving direction of a carriage when the loop is transferred from the transfer jack to the needle, for raising the loop retaining portion up to its raised position before the front side of the needle hook of the needle goes into the loop. With this construction of the present invention, when the loop is transferred from the TR jack to the needle, the clearing cam acts on the TR jack to push it down so as to push the loop retaining portion down before the back side of the needle hook of the needle goes into the loop, and, then, the raising cam acts on the TR jack to put it up so as to push the loop retaining portion up to its raised position before the front side of the needle hook goes into the loop.
It is one characteristic feature of the present invention that the raised position is set at a position at which an upper yarn portion of the loop retained on the loop retaining portion is located above an advancing-and-retracting track of the front side of the needle hook, and the lowered position is set at a position at which a lower yarn portion of the loop retained on the loop retaining portion is located below an advancing-and-retracting track of the back side of the needle hook. With the construction of the present invention, the needle hook advancing toward the loop is allowed to surely go into the loop without colliding with the lower yarn portion of the loop crossing beneath the loop retaining portion and the upper yarn portion of the loop crossing over the loop retaining portion.
Also, it is one characteristic feature of the present invention that the transfer jack control means comprises the clearing cam, located at a rear side of the raising cam with respect to a traveling direction of the carriage when the loop is transferred from the transfer jack to the needle, for controlling the loop retaining portion so as to be moved down to its lowered position when the TR jack is retracted from the loop. With this construction of the present invention, when the loop is transferred from the TR jack to the lower needle bed, the loop is lowered in position when the TR jack is retracted from the loop received by the needle. This enables the burden put on the loop to be reduced, and as such can provide the smooth transfer of the loop. Also, the TR jack is retracted from the loop in the condition that the loop is moved from the front side of the needle to the back side of the needle. This enables the loop to be reliably retained by the needle hook.
Also, the present invention provides a loop transfer method using a flat knitting machine with a loop transfer mechanism comprising a pair of front and back needle beds holding needles in such a manner as to freely advance and retract in grooves formed in upper surfaces of the needle beds, at least one of which is movable laterally relative to the other needle bed, and at least one transfer jack bed provided over the at least one needle bed and holding transfer jacks in such a manner as to freely advance and retract in grooves formed in upper surface of the at least one transfer jack bed, wherein when a loop is transferred from the transfer jack to the needle, the loop retaining portion of the transfer jack put in its advanced position is moved down to its lowered position, first; then, a back side of a needle hook of the needle is made to go into the loop retained on the loop retaining portion of the transfer jack; then the loop retaining portion is raised up to its raised position; and thereafter, a front side of the needle hook of the needle is made to go into the loop, whereby the needle hook is made to go into the loop retained on the loop retaining portion of the transfer jack.